The capability of selected pharmaceuticals to act as nontraditional endocrine disrupting chemicals in the environment has been poorly documented. The widely prescribed antidiabetic metformin has the potential to accumulate and persist in water bodies, with unknown consequences for aquatic biota. This study reports the biological responses of a sentinel organism, common mussel Mytilus edulis, exposed to concentrations of metformin commonly found in the aquatic environment, coupled with heat stress. The results indicate that metformin has the potential to increase the vitellogenin mRNA expression, to inflict severe pathologies of the gonad and to destabilize the lysosomal membrane in the hemocytes. Overall, this article suggests that metformin should be considered an emerging contaminant of concern and further research should focus on its mechanisms of action.

Qualitative and quantitative histological and histochemical techniques were used to study seasonal dynamics of energy reserves associated with gonad development and oocyte quality in the horsemussel Modiolus capax in Bahía de La Paz during the period February 2013 to January 2014. Thirty adult mussels were collected on a monthly basis and evaluated for gonad developmental stages and changes in oocyte features (theoretical diameter, nucleus/cytoplasm ratio, lipid index, and carbohydrate index). The overall somatic coverage area versus gonad coverage area and energy reserves in the gonad (carbohydrates and neutral lipids) was also analyzed. In summer (26.5 ± 1.4°C and 2.3 ± 0.7 mg m^-3 chlorophyll a), oocytes achieved greater sizes that were significantly correlated with higher lipid reserves in the gonad. This suggests that female gonads have superior breeding capacity in summer, compared with those in the autumn and winter periods, when oocyte performance and ovarian energy reserves were minimal. The evidence indicates that M. capax follows a conservative strategy to sustain gametogenesis relying on energy reserves previously stored in somatic tissue between autumn and winter. By contrast, optimal reproductive performance between April and August associates more with decreasing somatic coverage area and increasing gonad coverage area; this reflects a period of energy (lipids) transfer from storage tissues to the gonad to fuel gametogenesis. These results help establish the biological basis for gonad conditioning and maturation of M. capax to ensure continuous production of spat at the laboratory.

The golden mussel (Limnoperna fortunei), a mollusc originating from Asia, has caused considerable environmental and economic damage in various Brazilian river basins and reservoirs. Genetic studies that focus on characterizing its invasive potential and the feasibility of control measures are required. The present study identified and characterized 13 new microsatellite markers (of which eight were polymorphic) in L. fortunei using enriched genetic libraries. The analysis performed on 48 individuals from three populations identified 32 alleles, ranging from one to seven alleles per locus. The size of the fragments ranged from 172 to 381 bp. The polymorphic information content values ranged from 0.114 to 0.768, with observed and expected heterozygosity values ranging from 0.043–0.938 to 0.123–0.805, respectively. Six loci showed significant deviation from the Hardy–Weinberg equilibrium, possibly influenced by the heterozygous deficit. The microsatellite primers developed will be useful in studies of the genetic diversity and population structure of L. fortunei and will also contribute to the adoption of control measures for this invasive species in Brazilian and other South American basins.

Natural stocks of the Asian clam Corbicula fluminea (Müller, 1774) provide an important food source predominantly in Southern Asia. It is, therefore, important not only to assess the sustainability of natural stocks, but also to facilitate aquaculture efforts of this species. This study investigated the growth and survival rate of C. fluminea in bottom net culture over 13 mo in Çine Creek, Aydın, Turkey, in a temperate Mediterranean climate zone. Water temperature ranged between 10 and 24°C and food availability (measured by concentrations of chlorophyll-a (Chl-a) and suspended particulate organic matter) peaked during the autumn and spring. The final shell length (SL) and total body weight of C. fluminea (mean ± SE) were 29.02 ± 0.5 mm (initially 23.76 mm) and 12.17 ± 0.5 g (initially 6.65 g), respectively. Maximum growth rates were significantly higher during the autumn and spring months. A strong positive correlation was found between the availability of food (Chl-a) and total particulate matter concentrations and growth rates (in terms of SL and total weight). Survival was high (97%) by the end of the study and environmental conditions in Çine Creek supported good growth of clams. The species Corbicula fluminea, either as a native or introduced species, can be considered as a promising candidate species for the diversification of aquaculture in the region.

Microcystins (MC) produced by several cyanobacteria are potent hepatotoxins, whereas the toxicokinetics and subsequent detrimental effects ofMCare not fully understood in marine bivalves. In this study, the accumulation and depuration pattern of MC-Leucine-Arginine (MC-LR) along with the antioxidant response were investigated in the gill tissue of Pacific oyster Crassostrea gigas and blue mussel Mytilus edulis exposed to 0.1, 1, 10, and 20 µg L^-1 MC-LR for 7 days. Time- and concentration-dependent accumulation and depuration of MC-LR were observed in the gill tissue during the exposure and depuration phases. The values for maximum accumulation of MC-LR and malondialdehyde content were statistically significant (P < 0.05) at the end of exposure (day 7) to 20 µg L^-1 MC-LR for both the bivalves, and at the beginning of the depuration period when M. edulis and C. gigas were exposed to 10 and 20 µg L^-1, respectively. A significant level of glutathione (GSH) was detected in M. edulis in response to 20 µg L^-1 MC-LR during the exposure and depuration periods, whereas no significant levels of GSH were detected in C. gigas. The MC-LR accumulation induced oxidative stress in the gill tissue through modulation of the activities of antioxidant enzymes, the antioxidant response being more significant in the mussel than in the oyster. The enzymatic activities of glutathione S-transferase, superoxide dismutase (SOD), glutathione peroxidase, and glutathione reductase (GR) increased significantly in M. edulis, whereas in C. gigas, significant increase in the activities of SOD, catalase, and GR were observed at the end of exposure (day 7) to 20 µg L^-1 MC-LR. Similarly, during the depuration period, significant increases in the antioxidant activities were observed in M. edulis mostly at the beginning (day 1 and day 5) of exposure compared with the levels in C. gigas. The results obtained in this study will be useful in the understanding of MC-LR accumulation in bivalve gill tissues and the subsequent antioxidant defense response.

Eosinophilic Rickettsia-like organisms (E-RLO) were found for the first time in sick oysters of the species Crassostrea gigas, grown in Laguna de San Ignacio, Baja California Sur, Mexico, in August 2014. This work presents the histological description of development of bacteria in parasitophorous vacuoles of infected cells. Confirmative diagnosis was performed by polymerase chain reaction and in situ hybridization. Bacterial growth started with eosinophilic granules (colonial), followed by the formation and growth of intracytoplasmic inclusions. The presence of E-RLO was detected in the gill epithelium, mantle, labial palps, digestive tract, and both male and female gametes. This work describes for the first time an E-RLO in C. gigas with potential vertical transmission.

Relationships between shell morphological traits and byssus dimensions in adult winged pearl oysters Pteria penguin are described to include a more detailed description of byssus growth in juveniles under typical culture conditions. Byssus growth, byssus diameter (BD) relations between the byssus and shell traits [shell height; total wet weight (TW)], byssus occurrence, and the size distributions in samples collected monthly or bimonthly over a 1-y duration were recorded. Pearl oysters exhibited continuous shell growth and weight increase over the experimental period, but byssal measurements exhibited a different pattern. The increase in BD decreased as oysters aged and no further increase was observed after day 267. Moreover, BD/TW ratio exhibited a steadily diminishing trend as P. penguin aged. The relationships between the BD and the shell traits in 68-day-old oysters proved to be insignificant, probably because the oysters were neither heavy nor large enough to exhibit the relationships, but later, when oysters increased in size and weight, the relationships became significant. Byssus diameter was determined to be slightly more closely related to the weight of the animal than the size of the shell, and oysters at day 183 exhibited comparatively higher r2 values than oysters at day 366 of cultivation. The occurrence of oysters without byssus decreased gradually during cultivation from 30% initially to 0 after a year of cultivation.

The most common method for farming swimming crab Portunus trituberculatus in China is pond culture; however, their growth performance and ovarian development under these conditions are unclear. This study was conducted to investigate growth parameters, gonadosomatic index (GSI), hepatosomatic index, and monthly variation in the ovarian development of pond-reared female P. trituberculatus. The results showed (1) a significant increase in body weight (BW) and carapace width (CW) of female P. trituberculatus mainly during June to October, and the highest growth rate and specific growth rate of BW and CW were found during June to July. In addition, a significantly positive correlation was also found between BW and CW for pond-cultured P. trituberculatus females; (2) GSI increased significantly during ovarian development of pond-reared female P. trituberculatus and the mean GSI of ovarian stage I was 0.32%, whereas the mean GSI of ovarian stage V reached 7.92%; (3) Female P. trituberculatus started their pubertal molt at the end of July and the peak pubertal molt occurred from mid-August to early September; females nearly completed their pubertal molt in mid-October. Before pubertal molt, ovarian development of pond-reared P. trituberculatus was mainly at ovarian stage I during July to August; after the pubertal molt, females developed their ovaries quickly, with more than 80% at ovarian stage III inOctober. A second period of rapid ovarian development occurred at the end of January to the end of February, with a mean GSI reaching 5.25% at the end of February. From February to the end of March, no significant GSI changes were observed in female P. trituberculatus, indicating that the ovarian status of pond-reared female P. trituberculatus matured by the end of February.

Many decapod crustaceans inhabiting estuarine and coastal shores with larvae that develop in the coastal ocean release them at nocturnal ebb tides in a semilunar or lunar spring tide cycle under semidiurnal tidal regimes. In common brachyurans on warm temperate shores, this release cycle becomes first established in their mid-reproductive season. How this occurs is poorly understood, under the dichotomous views that peak larval release in each spring tide during the mid- to late season is timed to the syzygy date or the date with the largest tidal range (TR) and fastest tidal currents a few days later. The callianassid shrimp, Nihonotrypaea harmandi, inhabiting an intertidal sandflat in midwestern Kyushu, Japan, under a mixed, mainly semidiurnal, tidal regime has a reproductive season from June through October at water temperatures ranging from 20°C to 29°C. Frequent population sampling was conducted in 1993 (to mid-August) and 1994 (to early November), with cold and hot summers, respectively. Observations and experiments on embryo deposition and larval release, and measurement on water level and velocity were performed in other years. Harmonic analysis of tides was made on the water level and velocity and applied to those in 1994. Female shrimp released larvae at nocturnal ebb tides. The population comprised three age cohorts (one 2-y-old and two 1-y-old), and eight distinct larval releases occurred during June to October, each forming a batch preceded by embryo deposition by 3 wk to 2 wk linked to 20°C to ≥ 25°C in water temperature, respectively. Syzygy-centered peak embryo deposition first occurred in late July (for the third batch in 1994) and early August (for the fourth batch in 1993), with each batch dominated by the youngest cohort. Afterward, peak larval release immediately followed by peak embryo re-deposition every spring tide occurred in 1994. In the earlier reproductive season, the older two cohorts were dominant in the mature individuals, with a longer longevity of the oldest and more dominance of the second oldest in 1993 than in 1994, and embryo deposition was only weakly synchronized with syzygies, followed by longer embryo developmental durations. The peak larval release dates for the first two (in 1994) or three (in 1993) batches were between neap and spring tides. Thereafter, the peak date for each batch approached the largest-TR date but never coincided precisely. Seaward larval transport efficiency evaluated by the product of mean water velocity per ebb and ebb duration suggests suboptimal values throughout the reproductive season.

Early-stage larvae of the Kuruma shrimp Marsupenaeus japonicus are cultured up to mysis stages on microalgae, including Chaetoceros calcitrans, Chaetoceros gracilis, and/or Tetraselmis tetrathele, as food sources. Microalgal proliferation is affected by weather conditions, making stable and systematic production of both the microalgae and M. japonicus larvae difficult. The Thraustochytrids are a group of heterotrophic protists that include the genera Aurantiochytrium and Parietichytrium. The Thraustochytrids contain large quantities of n-3 highly unsaturated fatty acids, especially docosahexaenoic acid, an important nutritional component for the growth and physiological function of marine animals. Because the Thraustochytrids are heterotrophic and multiply rapidly in artificially controlled environments, their large scale culture is easy, stable, and systematic. To determine if Aurantiochytrium and Parietichytrium can be used instead of microalgae as a diet for early stage M. japonicus larvae, these larvae were reared in the laboratory on a diet containing C. calcitrans or strains of Aurantiochytrium or Parietichytrium, and their survival, development, and growth were compared. Larvae fed on the KOU10 strain of Parietichytrium sp. showed significantly greater survival, development, and growth than larvae fed on other diets, including those containing C. calcitrans. Although the mechanism by which the KOU10 strain enhanced the survival and growth performances of M. japonicus larvae is presently unclear, these larvae may be stably and systematically cultured on diets containing Parietichytrium instead of microalgae.

A feeding experiment was undertaken for 84 days to investigate the growth performance and the feed utilization of two horseshoe crab species from partial replacement of fish meal (FM) with blood meal (BM), meat and bone meal (MBM), and poultry by-product meal (PBM) in their diet. Triplicate groups of Tachypleus tridentatus or Carcinoscorpius rotundicauda were fed nine isonitrogenous (digestible protein 40%) and isoenergetic (digestible energy 14 MJ kg^-1) diet treatments. For both species, the growth performance, that is, final individual body weight and thermal-unit growth coefficient (TGC), and feed utilization, that is, including feeding rate (FR) and feeding efficiency ratio, of the juveniles fed with PBM and MBM at 2:1 ratio were higher than those of juveniles fed with diets containing PBM and MBM at 1:1 ratio at the same FM replacement level. Final individual body weight, TGC, and FR of the two species fed with the 100% FM replacement diets were significantly lower than in other diet treatments. The optimal replacement levels ofFMby the combination of PBM, MBM, andBMwere 50% and 75% in the protein of T. tridentatus and C. rotundicauda, respectively. Based on literature data, FM replacement reduced feed costs by 15%–25% in aquaculture practices.

The exploitation of bivalve molluscs in new fishing areas generally begins with scarce or no biological and fishery information to support management measures. The objective of this study was to estimate the morphometric relationships, growth parameters, and natural mortality in recently exploited populations of Megapitaria aurantiaca, Megapitaria squalida, and Dosinia ponderosa, to generate information on the population dynamics that could support management and conservation measures. The length–weight relationship and the relationships between the length, height, and width of the shells were calculated, which were used to estimate the morphometric size at first maturity. The parameters of the von Bertalanffy growth model were calculated through a modal progression analysis and the natural mortality was estimated depending on age. The morphometric relationships were allometric in all cases. The morphometric length at first maturity for M. aurantiaca is 67.60–77.20 mm, M. squalida is 35.40–40.32 mm, and D. ponderosa is 103.44 mm, which corresponds to ages between 0.68 and 5.97 y. The species exhibited a moderate growth (k = 0.421–0.448 y^-1). Natural mortality for the adult phase oscillated between 0.71 and 1.45 y^-1 and between 1.26 and 1.97 y^-1 during the juvenile phase. These estimates constitute basic inputs for fishery management and conservation of the species.

The market squid Doryteuthis opalescens deposits embryo capsules onto the continental shelf from Baja California to southern Alaska, yet little is known about the environment of embryo habitat. This study provides a baseline of environmental data and insights on factors underlying site selection for embryo deposition off southern California, and defines current essential embryo habitat using (1) remotely operated vehicle–supported surveys of benthos and environmental variables, (2) SCUBA surveys, and (3) bottom measurements of T, S, pH, and O₂. Here, embryo habitat is defined using embryo capsule density, capsule bed area, consistent bed footprint, and association with [O₂] and pH (pCO₂) on the shelf. Spatial variation in embryo capsule density and location appears dependent on environmental conditions, whereas the temporal pattern of year-round spawning is not. Embryos require [O₂] greater than 160 µmol and pH_T greater than 7.8. Temperature does not appear to be limiting (range: 9.9°C–15.5°C). Dense embryo beds were observed infrequently, whereas low-density cryptic aggregations were common. Observations of dense embryo aggregation in response to shoaling of low [O₂] and pH indicate habitat compression. Essential embryo habitat likely expands and contracts in space and time directly with regional occurrence of appropriate O₂ and pH exposure. Embryo habitat will likely be at future risk of compression given secular trends of deoxygenation and acidification within the Southern California Bight. Increasingly localized and dense spawning may become more common, resulting in potentially important changes in market squid ecology and management.

Previous research combining data on the abundance of benthic invertebrates living in the northernmost section of the Barnegat Bay-Little Egg Harbor estuary with data on water quality suggested a community composition consistent with anthropogenic eutrophication. This part of the estuary, however, experiences both high-nutrient and low-salinity environmental conditions, which are both ecologically stressful to sensitive species and favorable to opportunistic species, complicating assessments of the direct effects of anthropogenic eutrophication. Here, geohistorical baselines were derived from molluscan death assemblages from four localities along a north-south gradient in the bay—two northern low-salinity, high-nutrient sites and two southern high-salinity, low-nutrient sites—to disentangle the effects of salinity and nutrient enrichment on the composition of benthic communities. Disturbance in the northern section of the estuary from freshwater input has been relatively consistent for thousands of years, but nutrient enrichment is a more recent stressor, developing only in the past few decades. The cause of the disturbed benthic community is unlikely to be anthropogenic eutrophication, if there is little discordance between the living and the death assemblage in the northern, low-salinity section of the bay. Comparisons of rank-order abundance (Spearman's rho) and taxonomic similarity (Jaccard-Chao index) of the living and death assemblages along the north-south gradient, however, indicate that compositional shifts occur at the northern sites only. A multivariate index analysis, M-AMBI, which integrates the AZTI Marine Biotic Index, a biotic index based on species sensitivity/tolerance to disturbances, with Shannon diversity and species richness, shows a similar pattern: ecological status shifts (from undisturbed to disturbed) in the northern but not southern sites along the north-south salinity gradient. These independent lines of evidence corroborate the inference that it is most likely anthropogenic eutrophication (and not salinity) disturbance driving observed patterns in benthic community composition. Further sampling and incorporation of geohistorical data into ongoing benthic monitoring in the estuary is recommended to establish ecological baselines where none exist, guide restoration planning, and assess the success of restoration efforts.

Predation may be an important cause of early postsettlement mortality of bivalves, but little is known of in situ predation processes on bivalves by multiple predators on sandy beaches. To address this issue, bivalve shells in the guts of demersal fishes and benthic invertebrates were counted and measured monthly from April to November 2009 in Soma, Japan. For the Sakhalin surf clams Pseudocardium sachalinense and Raeta pulchella, the frequency of occurrence and number of shells in guts of predators per transect peaked around May–June, when the length of shells in guts tended to be smaller than in later months. These two indices decreased to 0 in July for P. sachalinense and to a low level in August for R. pulchella, which was associated with increasing shell length (ShL) in guts. For the bivalve Mactra crossei, both occurrence and number of shells in guts of predators per transect increased around November in some of the predators. The largest ShL of P. sachalinense in guts tended to be similar among the predators and was 1.1–1.5 mm. The largest ShL of R. pulchella and M. crossei tended to vary among the predators, and were 5.6–17.8 mm and 1.0–7.2 mm, respectively. The spiny sand sea star Luidia quinaria and red tongue sole Cynoglossus joyneri had a high frequency of occurrence and number of shells per gut per transect. These results indicate that predation on P. sachalinense and R. pulchella was most intense in the early postsettlement period of May–June in Soma, Japan. The size of the bivalve shell may have provided protection, but was dependent upon on the predator.

The environmental implications of integrated multitrophic aquaculture have been well studied in China, but few investigations have empirically explored potential economic benefits. This study investigated the technical and economic feasibility of physically integrating the noble scallop Mimachlamys nobilis (Reeve, 1852) with existing fish monoculture farms in Hong Kong. Scallops were grown for 201 days from June to December in lantern nets hung directly from fish farm platforms at treatment depths of 1, 3.5, and 6 m. Only the 1-m treatment attained the target mean height-at-harvest of 80 mm. Fitted von Bertalanffy growth functions showed significant differences in growth performance between depths. The von Bertalanffy growth function projected that the 3.5- and 6-m treatments would require an additional 26 and 59 days of culture to reach 80 mm. Mortality was significantly lower at 1 m (53% ± 12.5%) compared with those at 3.5 m (70% ± 9.0%) and 6 m (83% ± 4.5%). The slower growth and higher mortality at 3.5 and 6mwere probably due to periodically low oxygen which dropped to 4.96, 3.08, and 1.73 mg L^-1 at 1, 3.5, and 6 m, respectively, in midsummer. A bioeconomic assessments of two typical farm sizes was conducted; small (45 m²) and large (315 m²). The initial investment, discounted payback time, and 10-y net present value of the projects was US$5,485.51, 3 y, and US$20,211.33, respectively, for the small farm and US$27,659.03, 2 y, and US$227,406.49, respectively, for the large farm. Sensitivity analysis revealed that the profitability of operations was sensitive to changes in mortality and sales price. This study has confirmed that physically integrating M. nobilis at existing fish farms is technically and economically feasible.

The sea urchin Paracentrotus lividus is the most commercially important sea urchin species harvested in the NE Atlantic and Mediterranean coasts. To improve the management of P. lividus natural stock and its commercial exploitation, the population genetic structure of P. lividus in the Northeast Atlantic coast has been characterized. Populations from three regions of Spain: Asturias, Galicia, and the Canary Islands were sampled, and a 700-bp fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI) was sequenced. The obtained sequences were combined with previously available haplotypes coming from 127 sea urchins from the Canary Islands and the Mediterranean and Atlantic coasts of Spain—they collapsed in 54 haplotypes with 43 polymorphic sites—and 13 of these haplotypes were provided for the obtained sequences. The haplotype network shows high haplotype diversity and low nucleotide diversity values in all the studied populations. The distribution of analyzed haplotypes shows a high genetic homogeneity among populations. With the obtained data, no significant genetic differentiation could be found among populations analyzed in Galicia, Asturias, and the Canary Islands, and the existence of a population structure in this geographical area could not be determined. Based on this study, there would be no loss of genetic variability if the shores of the Canary Islands were repopulated with urchins from the Iberian Peninsula, although it is recommended to repopulate overexploited areas with urchins from the same zone until the study is extended with other molecular markers.

The sea urchin Mesocentrotus nudus is commercially harvested between June and August in northeastern Japan. A previous study showed that feeding on Saccharina japonica between April and June resulted in gonad quantity and quality improvement in this species from a barren. No information is available on the optimal culture period for harvest before the fishing season. The purpose of this study was to determine whether gonad size and quality (color, texture, and taste) can be improved before the fishing season and to verify the possibility of an early harvest. The sea urchins M. nudus were collected from a barren and placed under two types of culture conditions: suspended cages in a bay and a laboratory circulation system. They were fed S. japonica between December and May or March. Gonad indices, hardness, and color [L^*, a^*, and b^*, and ΔE_ab^* (a unit of acceptable commercial color difference from a fishing ground for each treatment)], and free amino acid (FAA) contents of the urchin gonads at the start of rearing experiments and at the end of cage (C) and laboratory feeding (LF) cultures were measured. These variables were also compared between LF and laboratory-starved urchins to confirm the dietary effect of this kelp. Gonad indices in treatments C and LF were significantly higher than those at the start of the experiment and those in laboratory starvation (P < 0.01), although there was no significant difference between C and LF. Gonads in treatment C were significantly softer than that at the start of the experiment (P < 0.0001). ΔE_ab^* of gonads in treatment C was the lowest, indicating that the gonad color was close to the preferred color. There was no significant difference in the total FAA content between C and LF treatments, whereas, of the umami FAA, glutamic acid content was significantly higher in gonads from C than LF. Of the bittertasting FAA, tyrosine and valine contents were significantly higher in LF gonads than in C gonads. These results suggested that gonad size, hardness, and color of M. nudus were improved before the fishing season by initiating culture in December with S. japonica feeding.